Protective enclosure for glass bulbs containing radioactive gas



Dec. 3, 1963 M. e. WRIGHT, JR 3,112,392

PROTECTIVE ENCLOSURE FOR GLASS BULBS CONTAINING RADIOACTIVE GAS Filed June 15, 1959 INVENTOR. MELWQIN G. WRIGHT,JR

BY ATTORNEY United States Patent 3,112,892 PROTECTIVE ENCLOSURE FOR GLASS BULBS CONTAINING RADIOACTIVE GAS Melvin Wright, Jr., Cleveland, Ohio, assignor to Union Carb1de C0rporation, a corporation of New York Filed June 15, 1959, Ser. No. 820,435 5 Claims. (Cl. 240-102) This invention relates to a protective enclosure for glass bulbs which contain radioactive gas, and more pargcilarly, to such an enclosure for light transmitting One of the recent technological advances in the field of visible signalling and marking devices is the use of a phosphor-coated glass bulb which is filled with radioactive tritium gas for the production of visible light. The excitation of the phosphor by electron bombardment from the tritium gas produces a visible glow of sufficient intensity for use in such devices. Unfortunately, the use of tritium gas, as with all radioactive gases, gives rise to a possible radiation hazard, particularly if the bulb Were to be broken. Bulb breakage is a distinct possibility, in such devices, due to the conventional shapes which are employed in the manufacture of glass bulbs.

Accordingly, the principal object of the invention is to provide a portable shock-resistant protective enclosure for a radioactive gas containing bulb which will minimize the possibility of breakage thereof and subsequent loss of the gas.

Another object of the invention is to provide a protective enclosure for a radioactive gas containing bulb which will insure effective retention of the radioactive gas in the event of bulb breakage.

A further object of the invention is to provide a transparent protective enclosure for a radioactive gas containing bulb which will not reduce the transmission of light therefrom.

Broadly stated, the objects of the invention are accomplished by a protective enclosure which comprises a generally U-shaped transparent plastic member which partially matches the contour of a generally spherical shaped radioactive gas filled bulb, a resilient collar which supports the neck of the bulb and a plastic member which protectc the .tip of the bulb.

The invention will be more readily understood by reference to the accompanying drawing wherein the single FIGURE is a side elevational view of a signalling device which employs the protective enclosure of the invention.

Referring now to the drawing, the protective enclosure comprises a generally U-shaped member made from a highly transparent plastic material having good impact resistance properties. A suitable plastic material for such use is one made from a methyl-methacrylate resin which is commercially available under the trademark Lucite. The plastic U-shaped member 10 is highly polished on both sides and shaped to match the contour of approximately 180 of the spherical portion 12 of a generally spherical shaped radioactive gas tilled bulb 14. A collar 16 of resilient material, such as sponge rubber, is recessed in and extends across the U-shaped member 10 and 7 supports and protects the neck 18 of the bulb 14. To complete the protective enclosure a plastic plug 20, preferably also made from the same methyl-methacrylate resin,

3,112,892 Patented Dec. 3, 1963 having a recess 22 to receive the tip 24 of the bulb 14, is hermetically sealed within the open end of the cup shaped member 10. Such sealing may be accomplished by solvent welding when both the U-shaped member 10 and the plug 20 are of the same material. In solvent welding, separate pieces of the same material are bonded together by dissolving a small amount of the same material in a suitable solvent, applying the solution to the parts to be joined, and subsequently allowing the solvent to evaporate. Preferably, a reflector 26, suitably of aluminum foil, is provided between the bulb 14 and the collar 16 to reflect the light emitting from the bulb 14.

All that is necessary to have a complete signalling device is to mount a reflector 28, suitably of spun aluminum, on the protective enclosure of the invention in such a manner as to reflect the most possible light which is emitted by the bulb 14. Optionally, a plastic shield 30, preferably also made from a methyl-methacrylate resin, may be placed across the face of the reflector 28.

It may be seen from the above description that the radioactive gas filled bulb is extremely well protected from breakage. In the event that it is broken, due to extremely rough handling or the like, the radioactive gas contained therein would be entrapped within the surrounding hermetically sealed protective plastic barrier, from where it could easily and safely be recovered.

I claim:

1. In combination, a completely independent, self exciting, radioactive gas-containing, generally spherical glass bulb provided with a neck portion which converges to a tip, and a protective enclosure therefore which comprises a generally U-shaped member of transparent impact resistant plastic, a collar of resilient material recessed in and extending across said U-shaped member, and a plastic plug provided with a recess therein which hermetically seals the open end of said U-shaped member; said bulb contained within said enclosure in such a manner that approximately of said spherical portion of said bulb is co-extensive with said U-shaped member, said neck portion is supported by said resilient collar, and said tip resides in said recess provided in said plastic plug.

2. The combination of claim 1 wherein a reflector is provided between said bulb and said collar.

3. The combination of claim 2 wherein said generally U-shaped plastic member and said plastic plug are a highly polished methyl-methacrylate resin, said resilient material is sponge rubber, and said reflector is aluminum foil.

4. A signalling device which comprises a completely independent, self-exciting, phosphor coated, radioactive gas-containing, generally spherical glass bulb provided with a neck portion which converges to a tip; a protective enclosure for said bulb which comprises a generally U-shaped member of transparent impact resistant plastic, a collar of resilient material recessed in and extending across said U-shaped member, and a plastic plug provided with a recess therein which hermetically seals the open end of said U-shaped member, said bulb contained within said enclosure in such a manner that approximately 180 of said spherical portion of said bulb is co-extensive with said U-shaped member, said neck portion is supported by said resilient collar, and said tip resides in References Cited in the file of this patent UNITED STATES PATENTS Benjamin Dec. 26, 1916 Flanuery Aug. 13, 1918 Popp et a1. July 4, 1950 McDowell Nov. 13, 1951 Schwinn Dec. 18, 1951 Smith Oct. 14, 1952 Johnson Nov. 11, 1958 

1. IN COMBINATION, A COMPLETELY INDEPENDENT, SELFEXCITING, RADIOACTIVE GAS-CONTAINING, GENERALLY SPHERICAL GLASS BULB PROVIDED WITH A NECK PORTION WHICH CONVERGES TO A TIP, AND A PROTECTIVE ENCLOSURE THEREFORE WHICH COMPRISES A GENERALLY U-SHAPED MEMBER OF TRANSPARENT IMPACT RESISTANT PLASTIC, A COLLAR OF RESILIENT MATERIAL RECESSED IN AND EXTENDING ACROSS SAID U-SHAPED MEMBER. 